Transmission for a motor vehicle

ABSTRACT

A transmission (G) for a motor vehicle includes an electric machine (EM 1 ), a first input shaft (GW 1 ), a second input shaft (GW 2 ), an output shaft (GWA), three planetary gear sets (P 1 , P 2 , P 3 ), and at least six shift elements (A, B, C, D, E, F). Different gears are implementable by selectively actuating the at least six shift elements (A, B, C, D, E, F), and different operating modes are implementable by selectively actuating the at least six shift elements (A, B, C, D, E, F) in interaction with the electric machine (EM 1 ). A drive train for a motor vehicle with the transmission (G) and a method for operating the transmission (G) are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related and has right of priority to GermanPatent Application No. 102018219624.9 filed in the German Patent Officeon Nov. 16, 2018 and is a nationalization of PCT/EP2019/077681 filed inthe European Patent Office on Oct. 14, 2019, both of which areincorporated by reference in their entirety for all purposes.

FIELD OF THE INVENTION

The invention relates generally to a transmission for a motor vehicle.Moreover, the invention relates generally to a motor vehicle drivetrain, in which the transmission is utilized, and to a method foroperating the transmission.

BACKGROUND

In the case of hybrid vehicles, transmissions are known which alsoinclude, in addition to a gear set, one or multiple electric machine(s).In this case, the transmission is usually configured to be multi-stage,i.e., multiple different ratios are selectable, as gears, between aninput shaft and an output shaft by actuating appropriate shift elements,wherein the gear shifts are preferably automatically carried out.Depending on the arrangement of the shift elements, the shift elementsare clutches or also brakes. The transmission is utilized in this casefor suitably implementing an available tractive force of a prime moverof the motor vehicle with respect to various criteria. In this case, thegears of the transmission are mostly also utilized in interaction withthe at least one electric machine for implementing purely electricdriving. Frequently, the at least one electric machine can also beintegrated in the transmission in order to implement various operatingmodes in different ways.

DE 10 2014 218 610 A1 describes a transmission for a hybrid vehicle,which includes, in addition to a first input shaft and an output shaft,three planetary gear sets and an electric machine. Moreover, in onevariant, six shift elements are provided, via which different powerpaths are achieved from the first input shaft to the output shaft whileimplementing different gears and, in addition, different integrations ofthe electric machine can be configured. Here, purely electric drivingcan also be implemented simply by transmitting power via the electricmachine.

BRIEF SUMMARY OF THE INVENTION

Example aspects of the present invention provide an alternative to thetransmission for a motor vehicle known from the prior art, with which,with a compact design, different operating modes can be implemented in asuitable way.

According to example aspects of the invention, a transmission includesan electric machine, a first input shaft, a second input shaft, anoutput shaft, as well as a first planetary gear set, a second planetarygear set, and a third planetary gear set. The planetary gear setsinclude multiple elements, wherein, preferably, a first element, asecond element, and a third element are associated with each of theplanetary gear sets. In addition, a first shift element, a second shiftelement, a third shift element, a fourth shift element, a fifth shiftelement, and a sixth shift element are provided, via the selectiveactuation of which different power paths are implementable whileshifting different gears. It is particularly preferred when at leastfour different gears can be formed, by the ratio, between the firstinput shaft and the output shaft. Moreover, a rotor of the electricmachine is connected to the second input shaft.

Within the meaning of the invention, a “shaft” is understood to be arotatable component of the transmission, via which associated componentsof the transmission are rotationally fixed to each other or via which aconnection of this type is established upon actuation of an appropriateshift element. The particular shaft can connect the components to eachother axially or radially or also both axially and radially. Theparticular shaft can also be present as an intermediate piece, via whicha particular component is connected, for example, radially.

Within the meaning of the invention, “axially” means an orientation inthe direction of a longitudinal central axis, along which the planetarygear sets are arranged coaxially to one another. “Radially” is thenunderstood to mean an orientation in the direction of the diameter of ashaft that lies on this longitudinal central axis.

Preferably, the output shaft of the transmission includes a toothsystem, via which the output shaft is then operatively connected, in themotor vehicle drive train, to a differential gear arranged axiallyparallel to the output shaft. In this case, the tooth system ispreferably provided at a mounting interface of the output shaft, whereinthis mounting interface of the output shaft is preferably situatedaxially in the area of an end of the transmission, at which a mountinginterface of the first input shaft is also provided, the mountinginterface establishing the connection to the upstream prime mover. Thistype of arrangement is particularly suitable for the application in amotor vehicle with a drive train aligned transversely to the directionof travel of the motor vehicle.

Alternatively, an output of the transmission can also be provided, inprinciple, at an axial end of the transmission situated opposite to amounting interface of the first input shaft. In this case, a mountinginterface of the output shaft is then designed at an axial end of theoutput shaft coaxially to a mounting interface of the first input shaft,so that the input and the output of the transmission are located atopposite axial ends of the transmission. A transmission configured inthis way is suitable for the application in a motor vehicle with a drivetrain aligned in the direction of travel of the motor vehicle.

According to a first example variant, the planetary gear sets arepreferably arranged in the sequence first planetary gear set, secondplanetary gear set, and, finally, third planetary gear set axiallyfollowing the mounting interface of the first input shaft. Within thescope of an alternative, second example variant of the invention,however, the planetary gear sets are located axially in the sequencethird planetary gear set, second planetary gear set, and, finally, firstplanetary gear set.

Example aspects of the invention now encompasses the technical teachingthat the first input shaft is rotationally fixed to the second elementof the first planetary gear set. The output shaft is rotationally fixedto the second element of the third planetary gear set. The first elementof the first planetary gear set and the first element of the thirdplanetary gear set are fixed at a rotationally fixed component.

With respect to the third planetary gear set, two couplings exist. Afirst coupling exists between the first element of the second planetarygear set and the rotationally fixed component. A second coupling existsbetween the second element of the second planetary gear set and thethird element of the third planetary gear set. A third coupling existsbetween the third element of the second planetary gear set and thehousing-affixed component. It is essential that, of these couplings, twocouplings are present as rotationally fixed connections, while theremaining coupling is establishable as a rotationally fixed connectionvia the first shift element.

Moreover, the second shift element is designed for rotationally fixingthe output shaft to the first input shaft. The third shift element isdesigned for rotationally fixing the output shaft to the third elementof the first planetary gear set. The fourth shift element is designedfor rotationally fixing the first input shaft to the third element ofthe third planetary gear set. The fifth shift element is designed forrotationally fixing the first input shaft to the second input shaft.

The sixth shift element is designed for interlocking the secondplanetary gear set or connecting the second input shaft to the thirdelement of the third planetary gear set. If one planetary gear set isinterlocked, the ratio is always one regardless of the number of teeth.In other words, the planetary gear set revolves as a block.

For example, the sixth shift element can be arranged and designed insuch a way that, in the actuated condition, the sixth shift elementconnects the first element with the second element of the secondplanetary gear set. However, the sixth shift element can also bearranged and designed in such a way that, in the actuated condition, thesixth shift element connects the first element with the third element ofthe second planetary gear set. The sixth shift element can also bearranged and designed in such a way that, in the actuated condition, thesixth shift element connects the second element with the third elementof the second planetary gear set.

The second shift element, the third shift element, the fourth shiftelement, the fifth shift element, and the sixth shift element arepresent as clutches, which, upon actuation, each synchronize, ifnecessary, the particular components of the transmission joined directlyto the clutches, with respect to their turning motions and, thereafter,connect the components to each other in a rotationally fixed manner.However, the first shift element is designed as a clutch or designed asa brake, depending on the variant, which, upon actuation, deceleratesthe components joined directly thereto to a standstill, if necessary,and, thereafter, fixes them.

A particular rotationally fixed connection of the rotatable componentsof the transmission is preferably implemented, according to exampleaspects of the invention, via one or also multiple intermediateshaft(s), which can also be present, in this case, as short intermediatepieces when the components are positioned in a spatially dense manner.Specifically, the components that are permanently rotationally fixed toeach other can each be present either as individual components that arerotationally fixed to each other, or also as single pieces. In thesecond case mentioned above, the particular components and theoptionally present shaft are then formed by one common component,wherein this is implemented, in particular, for the case in which theparticular components are situated spatially close to one another in thetransmission.

In the case of components of the transmission that are rotationallyfixed to each other only upon actuation of a particular shift element, aconnection is also preferably implemented via one or also multipleintermediate shaft(s).

A fixation takes place, in particular, by way of a rotationally fixedconnection to a rotationally fixed component of the transmission, whichis preferably a permanently non-rotating component, preferably a housingof the transmission, a part of such a housing, or a componentrotationally fixed thereto.

Within the meaning of the invention, the “connection” of the rotor ofthe electric machine to the second input shaft of the transmission is tobe understood as a connection of such a type that a constantrotational-speed dependence prevails between the rotor of the electricmachine and the second input shaft.

Overall, a transmission according to example aspects of the invention isdistinguished by a compact design, low component loads, good gearingefficiency, and low losses.

According to one example embodiment of the invention, the first shiftelement is arranged and designed in such a way that, in the actuatedcondition, the first shift element fixes the first element of the secondplanetary gear set at the rotationally fixed component, whereas thesecond element of the second planetary gear set is permanently connectedto the third element of the third planetary gear set in a rotationallyfixed manner and the third element of the second planetary gear set ispermanently connected to the second input shaft in a rotationally fixedmanner.

In this example variant, the second input shaft is therefore permanentlyrotationally fixed to the third element of the second planetary gearset, whereas the third element of the third planetary gear set ispermanently connected to the second element of the second planetary gearset in a rotationally fixed manner. In addition, an engagement of thefirst shift element results in a rotationally fixed connection betweenthe first element of the second planetary gear set with a rotationallyfixed component.

According to an alternative example design option of the invention, thefirst shift element is arranged and designed in such a way that, in theactuated condition, the first shift element connects the third elementof the second planetary gear set with the second input shaft in arotationally fixed manner, whereas the first element of the secondplanetary gear set is permanently fixed at the rotationally fixedcomponent and the second element of the second planetary gear set ispermanently connected with the third element of the third planetary gearset in a rotationally fixed manner.

In this coupling example variant, a permanently rotationally fixedconnection therefore exists between the first element of the secondplanetary gear set and the rotationally fixed component. In addition,the second element of the second planetary gear set and the thirdelement of the third planetary gear set are permanently connected toeach other in a rotationally fixed manner. The first shift element, uponactuation, connects the third element of the second planetary gear setand the second input shaft to one another in a rotationally fixedmanner.

In a further coupling example variant, the first shift element isarranged and designed in such a way that, in the actuated condition, thefirst shift element connects the second element of the second planetarygear set with the third element of the third planetary gear set in arotationally fixed manner, whereas the first element of the thirdplanetary gear set is permanently fixed at the rotationally fixedcomponent. The third element of the second planetary gear set ispermanently connected with the second input shaft in a rotationallyfixed manner.

In this example coupling variant, a permanently rotationally fixedconnection therefore exists between the first element of the secondplanetary gear set and the rotationally fixed component. In addition,the third element of the second planetary gear set and the second inputshaft are permanently connected to each other in a rotationally fixedmanner. The first shift element, upon actuation, permanently connectsthe third element of the third planetary gear set and the second elementof the second planetary gear set to one another in a rotationally fixedmanner.

According to one example embodiment of the invention, selectiveengagement of the six shift elements results in four gears between thefirst input shaft and the output shaft that differ in terms of ratio.

A first gear can be implemented between the first input shaft and theoutput shaft by actuating the first shift element and the fifth shiftelement, in which travel takes place with the simultaneous integrationof a prime mover joined at the first input shaft, and the electricmachine.

Moreover, a second gear results between the first input shaft and theoutput shaft in four variants. In a first example variant, the secondgear results by actuating the first shift element and the fourth shiftelement. In a second example variant, the second gear results byengaging the fourth shift element and the sixth shift element. In athird example variant, the second gear results by engaging the fifthshift element and the sixth shift element. Finally, the second gearresults, in a fourth example variant, by engaging the fourth shiftelement and the fifth shift element.

A third gear can be implemented between the first input shaft and theoutput shaft in a first example variant by engaging the first shiftelement and the second shift element. In addition, the third gear can beimplemented in a second example variant by engaging the second shiftelement and the sixth shift element. In a third example variant, thethird gear can be implemented by engaging the second shift element andthe fifth shift element.

In addition, in a fourth example variant, the third gear can beimplemented simply by engaging the second shift element, since the firstinput shaft and the output shaft are then directly connected to eachother in a rotationally fixed manner in combination with a rotationallyfixed connection of the output shaft with the second element of thefirst planetary gear set, and so travel can take place via the upstreamprime mover. The electric machine can also be decoupled, since, in thiscase, only the second shift element is loaded with torque and, inaddition, the second input shaft can remain idle. As a result, zero-loadlosses of the electric machine can be avoided. However, a shift into theaforementioned example variants of the third gear has the advantage thatthe electric machine is also integrated and, as a result, hybrid drivingcan take place.

A fourth gear can also be engaged between the first input shaft and theoutput shaft in a first example variant by actuating the first shiftelement and the third shift element. In a second example variant, thefourth gear can be selected by actuating the third shift element and thesixth shift element. Finally, in a third example variant, the fourthgear can be implemented by actuating the third shift element and thefifth shift element.

In addition, in a fourth example variant, the fourth gear can take placesimply by engaging the third shift element via the upstream prime mover,since, when the third shift element is engaged, the first input shaftand the output shaft are directly connected to each other in arotationally fixed manner in combination with a rotationally fixedconnection of the output shaft with the third element of the firstplanetary gear set. The electric machine can also be decoupled in thiscase, since, when the third shift element is engaged, only the thirdshift element is loaded with torque and the second input shaft canremain idle. Consequently, zero-load losses of the electric machine canbe avoided in the fourth gear. An implementation of four aforementionedexample variants of the fourth gear has the advantage, however, thathybrid driving can take place due to the simultaneous integration of theupstream prime mover and the electric machine.

Given a suitable selection of stationary transmission ratios of theplanetary gear sets, a transmission ratio range which is suitable forthe application in a motor vehicle is implemented as a result. In thiscase, gear shifts between the gears can be implemented, in which onlythe condition of two shift elements, in each case, is always to bevaried, in that one of the shift elements contributing to the precedinggear is to be disengaged and another shift element is to be engaged inorder to implement the subsequent gear. As a further consequencethereof, a shift between the gears can take place very rapidly.

Due to the connection of the electric machine to the second input shaftof the transmission, different operating modes can also be achieved in asimple way.

A first gear between the second input shaft and the output shaft can beutilized for purely electric driving, wherein this first gear results byengaging the first shift element.

By engaging the first shift element, the electric machine is connectedto the drive output with a constant ratio (the third element withrespect to the second element in each case with a fixed first element ofthe second planetary gear set and the third planetary gear set), i.e.,travel then takes place purely electrically with a ratio thatcorresponds to the first internal combustion engine-driven gear.

In addition, a second gear can also be implemented between the secondinput shaft and the output shaft for purely electric driving. The sixthshift element is to be actuated in order to engage this second gear. Byengaging the sixth shift element, the electric machine is connected tothe drive output with a constant ratio (the third element transmits ontothe second element with the first element of the third planetary gearset fixed), i.e., travel then takes place purely electrically with aratio that corresponds to the second gear.

Starting from purely electric driving in the first gear, which iseffective between the second input shaft and the output shaft, theupstream prime mover can then be started into the first gear, which iseffective between the first input shaft and the output shaft. Inaddition, the start can take place into the first example variant of thesecond gear. Finally, the start can take place into the first examplevariant of the third gear. In addition, the start can take place intothe first example variant of the fourth gear. The first shift elementcontributes to each of these gears.

In addition, a start of the upstream prime mover can also take placefrom the second gear, which is effective between the second input shaftand the output shaft, into the second example variant of the secondgear, into the third example variant of the second gear, into the secondexample variant of the third gear, and into the second example variantof the fourth gear, which is effective between the first input shaft andthe output shaft.

As a further operating mode, a charging operation of an electricaccumulator can also be implemented, in that only the fifth shiftelement is engaged and, thereby, a rotationally fixed connection betweenthe first input shaft and the second input shaft and, thereby, also acoupling to the electric machine are established. In this condition, thesecond input shaft rotates, in particular, faster than the first inputshaft. At the same time, a force-fit connection to the output shaft isnot established, and therefore the transmission is in a neutralposition. Apart from a charging operation, a start of the upstream primemover via the electric machine can also be implemented as a result.

Moreover, powershifts with tractive force support can be implemented.During the gearchange between the first gear and the second gear, thetractive force with the first shift element engaged can be supported viathe electric machine, wherein the synchronization of the shift elementto be engaged takes place via a closed-loop control of the rotationalspeed of the upstream prime mover. Alternatively, however, this can alsotake place by using synchronized shift elements or also by usinganother, separate synchronizing mechanism, such as a transmission brakeor also one further electric machine, which can be operatively connecteddirectly or indirectly to the first input shaft. If one further shiftelement, as a separating clutch, is also provided on the input side ofthe input shaft, the inertial mass of the upstream drive machine can bedecoupled during the synchronization.

A gearchange under load can also take place between the second gear andthe first example variant of the third gear when the first shift elementis engaged. This is also implementable, in addition, during a gearchangebetween the first example variant of the third gear and the firstexample variant of the fourth gear, which is effective between the firstinput shaft and the output shaft, since the first shift elementcontributes to both example variants in this case as well.

The transmission according to example aspects of the invention can alsobe operated in such a way that a rotational-speed reduction of theelectric machine is achieved during driving. It is therefore possible toinitially drive in a hybrid manner in the first example variant of thefourth gear, in that the first shift element initially remains engagedeither after a gear shift from the third gear into the fourth gear withtorque assistance from the electric machine or after a start of theprime mover into the fourth gear. In order to now reduce a rotationalspeed of the electric machine in the fourth gear at higher groundspeeds, however, a change-over can be carried out from the first examplevariant of the fourth gear into the second example variant of the fourthgear, since the rotor of the electric machine has a lower rotationalspeed in the second example variant of the fourth gear than in the firstexample variant of the fourth gear. This change-over takes place whileobtaining the tractive force via the upstream prime mover, with thethird shift element engaged. Initially, the load-free, first shiftelement is disengaged and, subsequent thereto, the load-free, sixthshift element is engaged, wherein the rotational-speed adaptation takesplace via closed-loop control of the rotational speed of the electricmachine.

A separate shift element is not necessary for decoupling the upstreamprime mover, since, in the second example variant of the fourth gear,which is effective between the first input shaft and the output shaft,the upstream prime mover can be decoupled by disengaging the third shiftelement. As a result, the second gear is then implemented, which iseffective between the second input shaft and the output shaft. Inaddition, in the case of a vehicle that is slowing down, a downshiftfrom the fourth gear, which is effective between the first input shaftand the output shaft, into the third gear, which is effective betweenthe first input shaft and the output shaft, can be prepared, in that,initially, a change-over takes place from the second example variantinto the first example variant of the fourth gear and, in the process,the tractive force is obtained via the upstream prime mover, with thethird shift element engaged. In the first example variant of the fourthgear, the first shift element is engaged, which becomes necessary inorder to support the tractive force via the electric machine as part ofthe downshift from the fourth gear into the third gear.

Alternatively, a downshift from the fourth gear, which is effectivebetween the first input shaft and the output shaft, into the third gear,which is effective between the first input shaft and the output shaft,can also be implemented with the sixth shift element engaged, however,in that a change-over takes place between the second example variant ofthe fourth gear and the second example variant of the third gear, to theimplementation of which the sixth shift element contributes, in eachcase. The electric machine then supports the tractive force. Thereafter,the sixth shift element can be disengaged, if necessary, and,subsequently, the first shift element can be engaged, wherein asynchronization takes place via the electric machine and a support ofthe tractive force takes place via the upstream prime mover. As aresult, the rotational speed of the electric machine can also be variedin the third gear, which is effective between the first input shaft andthe output shaft.

As one further example design option of the invention, a furtherelectric machine is provided, the rotor of which is connected at thefirst input shaft. In addition, as one further example design option ofthe invention, a further electric machine is provided, the rotor ofwhich is connected at the third element of the first planetary gear set.

Such an example embodiment has the advantage that further driving modescan be achieved as a result. In addition, as a result, a start of theupstream prime mover can be implemented immediately, if necessary, ifthe prime mover is designed as an internal combustion engine. Inaddition, the additional electric machine can support the upstream primemover in the synchronization of shift elements.

According to one further example embodiment of the invention, the firstinput shaft can be connected in a rotationally fixed manner, via aseventh shift element, to a connection shaft, which, in turn, is thenpreferably coupled within a motor vehicle drive train to the prime moverconnected upstream from the transmission. The seventh shift element canbe designed, in principle, as a force-locking or also as a form-lockingshift element in this case, although it is particularly preferred whenthe seventh shift element is present as a dog clutch. Via the seventhshift element, the upstream prime mover can therefore also be completelydecoupled from the transmission, so that a purely electric operation isimplementable in a problem-free manner.

In one example refinement of the invention, one or multiple shiftelement(s) is/are each implemented as a form-locking shift element. Inthis case, the particular shift element is preferably designed either asa constant-mesh shift element or as a lock-synchronizer mechanism.Form-locking shift elements have the advantage over friction-lockingshift elements that lower drag losses occur in the disengaged condition,and therefore a better efficiency of the transmission can be achieved.In particular, in the transmission according to example aspects of theinvention, all shift elements are implemented as form-locking shiftelements, and therefore the lowest possible drag losses can be achieved.In principle, however, one shift element or multiple shift elementscould also be configured as force-locking shift elements, for example,as lamellar shift elements.

The planetary gear sets are preferably arranged in the axial directionstarting from a transmission input in the sequence first planetary gearset, second planetary gear set, third planetary gear set.

Within the scope of example aspects of the invention, the planetary gearsets can each be present as a minus or negative planetary gear set,provided it allows for a connection of the elements, wherein the firstelement of the particular planetary gear set is a sun gear, the secondelement of the particular planetary gear set is a planet carrier, andthe third element of the particular planetary gear set is a ring gear. Aminus planetary gear set is composed, in a way known, in principle, to aperson skilled in the art, of the elements sun gear, planet carrier, andring gear, wherein the planet carrier, rotatably mounted, guides atleast one planet gear, although preferably multiple planet gears, whicheach individually mesh with the sun gear and with the surrounding ringgear.

Alternatively thereto, one planetary gear set or also multiple planetarygear sets could also be present as a plus or positive planetary gearset, however, provided it allows for the connection of the particularelements, wherein the first element of the particular planetary gear setis then a sun gear, the second element of the particular planetary gearset is a ring gear, and the third element of the particular planetarygear set is a planet carrier. In a plus planetary gear set as well, theelements sun gear, ring gear, and planet carrier are present, whereinthe planet carrier guides at least one planet gear pair, in which oneplanet gear is meshed with the internal sun gear and the other planetgear is meshed with the surrounding ring gear, and the planet gears areintermeshed with each other.

Where permitted by a connection of the individual elements, a minusplanetary gear set can be converted into a plus planetary gear set,wherein, as compared to the design as a minus planetary gear set, thering gear connection and the planet carrier connection are to beinterchanged, and a stationary transmission ratio is to be increased byone. Conversely, a plus planetary gear set could also be replaced by aminus planetary gear set, provided the connection of the elements of thetransmission enables this. In this case, as compared to the plusplanetary gear set, the ring gear connection and the planet carrierconnection would also need to be interchanged, and a stationarytransmission ratio would need to be reduced by one. Within the scope ofexample aspects of the invention, the three planetary gear sets are eachpreferably designed as a minus planetary gear set, however.

In the present case, each planetary gear set can be designed as a minusplanetary gear set or as a plus planetary gear set, since a direct drivedoes not result at the second element of the second planetary gear set.

Each of the planetary gear sets is preferably present as a minusplanetary gear set, wherein the first element of the particularplanetary gear set is a sun gear, the second element of the particularplanetary gear set is a planet carrier, and the third element of theparticular planetary gear set is a ring gear. A minus planetary gear setis composed, in a way known, in principle, to a person skilled in theart, of the elements sun gear, planet carrier, and ring gear, whereinthe planet spider, rotatably mounted, guides at least one planet gear,although preferably multiple planet gears, which each individually meshwith the sun gear and with the surrounding ring gear, i.e., are inmeshing engagement therewith.

According to one further example embodiment of the invention, the firstshift element and the sixth shift element are combined to form a shiftelement pair, with which one actuating element is associated. The firstshift element, on the one hand, and the sixth shift element, on theother hand, can be actuated via the actuating element starting from aneutral position. This has the advantage that, due to this combination,the number of actuating elements can be reduced and, thereby, themanufacturing complexity can also be reduced.

Alternatively or also in addition to the aforementioned examplevariants, the second shift element and the third shift element arecombined to form a shift element pair, with which one actuating elementis associated. The second shift element, on the one hand, and the thirdshift element, on the other hand, can be actuated from a neutralposition via this actuating element. As a result, the manufacturingcomplexity can be reduced, in that, due to the combination of the twoshift elements to form a shift element pair, one actuating unit can beutilized for both shift elements. Alternatively, the second shiftelement and the fourth shift element or the second shift element and thefifth shift element can also be combined, however.

In addition, alternatively or also in addition to the two aforementionedexample variants, the fourth shift element and the fifth shift elementare combined to form a shift element pair, with which one actuatingelement is associated. The fourth shift element, on the one hand, andthe fifth shift element, on the other hand, can be actuated via thisactuating element starting from a neutral position. As a result of thisas well, the manufacturing complexity can be reduced, since an actuationof the two shift elements can therefore take place via one commonactuating unit. Alternatively, the third shift element and the fifthshift element or the third shift element and the fourth shift elementcan also be combined, however.

It is particularly preferred when three aforementioned shift elementpairs are implemented simultaneously, and so the six shift elements ofthe transmission can be actuated via three actuating elements. As aresult, a particularly low manufacturing complexity can be achieved.

According to one example embodiment of the invention, the rotor of theelectric machine is rotationally fixed to the second input shaft.Alternatively, according to one example design option of the invention,the rotor is connected to the second input shaft via at least one gearstage. The electric machine can be arranged either coaxially to theplanetary gear sets or so as to be situated axially offset with respectthereto. In the former case, the rotor of the electric machine caneither be rotationally fixed directly to the second input shaft or canbe coupled thereto via one or also multiple intermediate gear stage(s),wherein the latter allows for a more favorable configuration of theelectric machine with higher rotational speeds and lower torques. The atleast one gear stage can be designed as a spur gear stage and/or as aplanetary gear stage in this case. In the case of a coaxial arrangementof the electric machine, one or more of the planetary gear set(s) canthen also, more preferably, be arranged axially in the area of theelectric machine as well as radially internally with respect thereto, sothat the axial installation length of the transmission can be shortened.

If the electric machine is provided axially offset with respect to theplanetary gear sets, however, a coupling takes place via one or multipleintermediate gear stage(s) and/or a flexible traction drive mechanism.The one or the multiple gear stage(s) can also be implementedindividually, in this case, either as a spur gear stage or as aplanetary gear stage. A flexible traction drive mechanism can be eithera belt drive or a chain drive.

If a further electric machine is also provided, a rotor of this furtherelectric machine can also be either rotationally fixed to the firstinput shaft directly or can be coupled to the first input shaft via atleast one gear stage. The at least one gear stage can be a spur gearstage or a planetary gear stage or also a flexible traction drivemechanism. In addition, the further electric machine can be providedcoaxially or also axially offset with respect to the first input shaftand, thereby, also to the planetary gear sets.

Within the scope of example aspects of the invention, a startingcomponent can be installed upstream from the transmission, for example ahydrodynamic torque converter or a friction clutch. This startingcomponent can then also be an integral part of the transmission and actsto configure a starting process, in that the starting component enablesa slip speed between the prime mover, which is designed, in particular,as an internal combustion engine, and the first input shaft of thetransmission. In this case, one of the shift elements of thetransmission or the separating clutch, which may be present, can also bedesigned as such a starting component, in that the one of the shiftelements is present as a frictional shift element. In addition, aone-way clutch with respect to the transmission housing or to anothershaft can be arranged on each shaft of the transmission, in principle.

The transmission according to example aspects of the invention is, inparticular, part of a motor vehicle drive train for a hybrid or electricvehicle and is then arranged between a prime mover of the motor vehicle,which is configured as an internal combustion engine or as an electricmachine, and further components of the drive train, which are arrangeddownstream in the direction of power flow to driving wheels of the motorvehicle. In this case, the first input shaft of the transmission iseither permanently coupled to a crankshaft of the internal combustionengine or to the rotor shaft of the electric machine in a rotationallyfixed manner or is connectable thereto via an intermediate separatingclutch or a starting component, wherein a torsional vibration damper canalso be provided between an internal combustion engine and thetransmission. On the output end, the transmission is then preferablycoupled, within the motor vehicle drive train, to a differential gear ofa drive axle of the motor vehicle, wherein a connection to an interaxledifferential can also be present in this case, however, via which adistribution to multiple driven axles of the motor vehicle takes place.The differential gear or the interaxle differential can be arranged withthe transmission in one common housing in this case. A torsionalvibration damper, which is optionally present, can also be integratedinto this housing.

Within the meaning of the invention, the expressions that two componentsof the transmission are “connected” or “coupled” or “are connected toeach other” mean a permanent coupling of these components, and thereforesaid components cannot rotate independently of each other. In thatrespect, no shift element is provided between these components, whichcan be elements of the planetary gear sets and/or also shafts and/or arotationally fixed component of the transmission. Instead, theappropriate components are coupled to each other with a consistentrotational speed dependence.

However, if a shift element is provided between two components, thesecomponents are not permanently coupled to each other. Instead, acoupling is carried out only by actuating the intermediate shiftelement. In this case, an actuation of the shift element means, withinthe meaning of the invention, that the particular shift element istransferred into an engaged condition and, consequently, synchronizesthe turning motions, if necessary, of the components connected directlythereto. In the case of an example embodiment of the particular shiftelement as a form-locking shift element, the components directlyconnected to each other in a rotationally fixed manner via the shiftelement rotate at the same rotational speed, while, in the case of aforce-locking shift element, speed differences can exist between thecomponents also after an actuation of the same shift element. Thisintentional or also unintentional condition is nevertheless referred to,within the scope of the invention, as a rotationally fixed connection ofthe particular components via the shift element.

The invention is not limited to the specified combination of features ofthe main claim or the claims dependent thereon. In addition, individualfeatures can be combined with one another, provided they arise from theclaims, the description of preferred embodiments of the invention whichfollows, or directly from the drawings. References in the claims to thedrawings via the use of reference signs is not intended to limit thescope of protection of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantageous example embodiments of the invention, which are explainedin the following, are represented in the drawings, in which:

FIG. 1 shows a diagrammatic view of a motor vehicle drive train;

FIGS. 2 through 7 each show a diagrammatic view of a transmission of thetype that can be utilized in the motor vehicle drive train from FIG. 1;

FIG. 8 shows an exemplary shift pattern of the transmissions from FIGS.2 to 7;

FIGS. 9 and 10 each show a diagrammatic view of a transmission of thetype that can also be utilized in the motor vehicle drive train fromFIG. 1;

FIG. 12 shows an exemplary shift pattern of the motor vehicle drivetrain from FIG. 1 with the transmission according to FIGS. 9 and 10; and

FIGS. 13 through 16 each show a schematic of a modification of thetransmissions from FIGS. 2 through 7 as well as 9 and 10.

DETAILED DESCRIPTION

Reference will now be made to embodiments of the invention, one or moreexamples of which are shown in the drawings. Each embodiment is providedby way of explanation of the invention, and not as a limitation of theinvention. For example, features illustrated or described as part of oneembodiment can be combined with another embodiment to yield stillanother embodiment. It is intended that the present invention includethese and other modifications and variations to the embodimentsdescribed herein.

FIG. 1 shows a diagrammatic view of a motor vehicle drive train of ahybrid vehicle, wherein, in the motor vehicle drive train, an internalcombustion engine VKM is connected to a transmission G via anintermediate torsional vibration damper TS. Connected downstream fromthe transmission G, on the output end thereof, is a differential gearAG, via which drive power is distributed to driving wheels DW of a driveaxle of the motor vehicle. The transmission G and the torsionalvibration damper TS are arranged in a common housing of the transmissionG in this case, into which the differential gear AG can then also beintegrated. As is also apparent in FIG. 1, the internal combustionengine VKM, the torsional vibration damper TS, the transmission G, andalso the differential gear AG are aligned transversely to a direction oftravel of the motor vehicle.

FIG. 2 shows a schematic of the transmission G according to a firstexample embodiment of the invention. As is apparent, the transmission Gincludes a gear set RS and an electric machine EM1, which are botharranged in the housing of the transmission G. The gear set RS includesthree planetary gear sets P1, P2, and P3, wherein each of the planetarygear sets P1, P2, and P3 includes a first element E11 and E12 and E13,respectively, a second element E21 and E22 and E23, respectively, and athird element E31 and E32 and E33, respectively. The first element E11and E12 and E13 is formed by a sun gear of the planetary gear set P1 andP2 and P3, respectively, while the second element E21 and E22 and E23 ofthe planetary gear set P1 and P2 and P3, respectively, is present as aplanet carrier, and the third element E31 and E32 and E33 of theplanetary gear set P1 and P2 and P3, respectively, is present as a ringgear.

In the present case, the first planetary gear set P1, the secondplanetary gear set P2, and the third planetary gear set P3 are eachtherefore present as a minus planetary gear set. The particular planetcarrier thereof guides at least one planet gear in a rotatably mountedmanner; the planet gear is meshed with the particular radially internalsun gear as well as with the particular radially surrounding ring gear.It is particularly preferred, however, when multiple planet gears areprovided in the first planetary gear set P1, in the second planetarygear set P2, and also in the third planetary gear set P3.

As is apparent in FIG. 2, the transmission G includes a total of sixshift elements in the form of a first shift element A, a second shiftelement B, a third shift element C, a fourth shift element D, a fifthshift element E, and a sixth shift element F. These shift elements areeach designed as form-locking shift elements and are preferably presentas constant-mesh shift elements. While the first shift element A isdesigned as a brake, the remaining shift elements B, C, D, E, and F arepresent as clutches.

The first element E11 of the first planetary gear set P1 and the firstelement E13 of the third planetary gear set P3 are fixed at arotationally fixed component GG and, thereby, permanently prevented frommaking a turning motion. The rotationally fixed component GG is, inparticular, the transmission housing of the transmission G or a portionof the transmission housing. The second element E21 of the firstplanetary gear set P1 is permanently connected to a first input shaftGW1 in a rotationally fixed manner.

The second element E22 of the second planetary gear set P2 and the thirdelement E33 of the third planetary gear set P3 are permanently connectedto each other in a rotationally fixed manner. The second element E23 ofthe third planetary gear set P3 is connected to an output shaft GWA ofthe transmission G. The first element E13 of the second planetary gearset P2 can be fixed at the rotationally fixed component GG via the firstshift element A.

As is also apparent in FIG. 2, the first input shaft GW1 of thetransmission G can be connected with the output shaft GWA in arotationally fixed manner via the second shift element B.

Apart therefrom, the third element E31 of the first planetary gear setP1 can be brought into a rotationally fixed connection with the outputshaft GWA by engaging the third shift element C.

The first input shaft GW1 can also be connected with the third elementE33 of the third planetary gear set P3 in a rotationally fixed mannervia the fourth shift element D and can be connected with the secondinput shaft GW2 in a rotationally fixed manner by the fifth shiftelement E. Moreover, the second element E22 of the second planetary gearset P2 can be connected to the first element E12 of the second planetarygear set P2 in a rotationally fixed manner by engaging the sixth shiftelement F. If the sixth shift element F is actuated, the secondplanetary gear set P2 is interlocked.

The first input shaft GW1 as well as the output shaft GWA form amounting interface GW1-A and GWA-A, respectively, wherein the mountinginterface GW1-A in the motor vehicle drive train from FIG. 1 is utilizedfor a connection at the internal combustion engine VKM, while thetransmission G is connected at the mounting interface GWA-A to thedownstream differential gear AG. The mounting interface GW1-A of thefirst input shaft GW1 is formed at an axial end of the transmission G,while the mounting interface GWA-A of the output shaft GWA is situatedin the area of the same axial end and, here, is aligned transversely tothe mounting interface GW1-A of the first input shaft GW1. In addition,the first input shaft GW1, the second input shaft GW2, and the outputshaft GWA are arranged coaxially to one another.

The planetary gear sets P1, P2, and P3 are also situated coaxially tothe input shafts GW1 and GW2 and the output shaft GWA, wherein theplanetary gear sets P1, P2, and P3 are arranged in the sequence firstplanetary gear set P1, second planetary gear set P2, and third planetarygear set P3 axially subsequent to the mounting interface GW1-A of thefirst input shaft GW1. The electric machine EM1 is also locatedcoaxially to the planetary gear sets P1, P2, and P3 and, thereby, alsoto the input shafts GW1 and GW2 and the output shaft GWA, wherein theelectric machine EM1 is arranged axially at the level of the secondplanetary gear set P2 and of the third planetary gear set P3 andradially surrounding the second and third planetary gear sets P2, P3.

The sixth shift element F and the first shift element A are situatedaxially directly next to each other and radially at the same level andare combined to form a shift element pair SP1, in that a commonactuating element is associated with the first shift element A and thesixth shift element F, via which the sixth shift element F, on the onehand, and the first shift element A, on the other hand, can be actuatedfrom a neutral position.

The second shift element B and the third shift element C are alsolocated axially between the first planetary gear set P1 and the secondplanetary gear set P2. The second shift element B and the third shiftelement C are provided axially directly next to each other and radiallyat the same level and include a common actuating element, via which thesecond shift element B, on the one hand, and the third shift element C,on the other hand, can be actuated from a neutral position. In thatrespect, the second shift element B and the third shift element C arecombined to form a shift element pair SP2.

Finally, the fourth shift element D and the fifth shift element E aresituated axially on a side of the third planetary gear set P3 facingaway from the second planetary gear set P2. The fourth shift element Dand the fifth shift element E are combined to form a shift element pairSP3, in that the fourth and shift elements D, E are provided axiallydirectly next to each other and radially essentially at the same leveland include a common actuating element, via which the fourth shiftelement D, on the one hand, and the fifth shift element E, on the otherhand, can be actuated from a neutral position.

Moreover, FIG. 3 shows a diagrammatic view of a transmission G accordingto a second example design option of the invention, which can also beutilized in the motor vehicle drive train in FIG. 1. This example designoption largely corresponds to the preceding example variant according toFIG. 2, with the difference that the sixth shift element now designatedwith F′ (F prime), in the actuated condition, connects the first elementE12 with the third element E32 of the second planetary gear set P2 in arotationally fixed manner. Therefore, the example embodiment accordingto FIG. 3 is an interlock variant. Otherwise, the example design optionaccording to FIG. 3 corresponds to the example variant according to FIG.2, and therefore reference is made to the description thereof.

Moreover, FIG. 4 shows a diagrammatic view of a transmission G accordingto a second example design option of the invention, which can also beutilized in the motor vehicle drive train in FIG. 1. This example designoption largely corresponds to the preceding example variant according toFIG. 2, with the difference that the sixth shift element now designatedwith F″ (F double prime), in the actuated condition, connects the thirdelement E32 with the second element E22 of the second planetary gear setP2 in a rotationally fixed manner. Therefore, the example embodimentaccording to FIG. 4 is a second interlock example variant. Otherwise,the example design option according to FIG. 4 corresponds to the examplevariant according to FIGS. 2 and/or 3, and therefore reference is madeto the description thereof.

Starting from the second interlock variant (FIG. 4), two furthercoupling example variants are possible. This means, two further possibleexample arrangements of the first shift element A are conceivable. Inthe actuated condition, the first shift element A allows for a torquetransmission by the third planetary gear set P3. However, if the firstshift element A is disengaged, a torque transmission by the thirdplanetary gear set P3 is not possible, since torque support cannot takeplace at the first element E12.

FIG. 5 shows a schematic of a transmission G according to a firstexample coupling variant of the invention, of the type which can also beutilized in the motor vehicle drive train from FIG. 1. In contrast tothe example embodiment according to FIG. 4, the first shift element nowdesignated as A′ (A prime) is not positioned at the first element E12,but rather at the third element E32. This means, the formerlypermanently fixed connection of the third element E32 with the secondinput shaft GW2 is replaced by a shiftable connection, and the formerlyshiftable connection of the first element E12 to the rotationally fixedcomponent GG is replaced by a fixed housing connection. If the firstshift element A′ (A prime) is actuated, torque can be supported via thefixed element E12. Otherwise, the example design option according toFIG. 5 corresponds to the example variant according to FIG. 4, andtherefore reference is made to the description thereof.

FIG. 6 shows a schematic of a transmission G according to a secondexample coupling variant of the invention, of the type which can also beutilized in the motor vehicle drive train from FIG. 1. In contrast tothe example embodiment according to FIG. 4, the first shift element nowdesignated as A″ (A double prime) is not positioned at the first elementE12, but rather at the second element E22. This means, the formerlypermanently fixed connection of the second element E22 with the thirdelement E33 is replaced by a shiftable connection, and the formerlyshiftable connection of the first element E12 to the rotationally fixedcomponent GG is replaced by a fixed housing connection. If the firstshift element A″ (A double prime) is actuated, torque can be supportedvia the fixed element E12. Otherwise, the example design optionaccording to FIG. 6 corresponds to the example variant according to FIG.4, and therefore reference is made to the description thereof.

FIG. 7 shows an exemplary shift pattern for the example transmissions Gfrom FIGS. 2 through 8 in table form. As is apparent, a total of fourgears 1 through 4, which differ in terms of the ratio, can beimplemented between the first input shaft GW1 and the output shaft GWA,wherein, in the columns of the shift pattern, an X indicates which ofthe shift elements A through F is engaged in which of the gears 1through 4.

As is apparent in FIG. 7, a first gear 1 is engaged between the firstinput shaft GW1 and the output shaft GWA by actuating the first shiftelement A and the fifth shift element E.

Moreover, a second gear 2 results between the first input shaft GW1 andthe output shaft GWA in a first example variant 2.1 by engaging thefirst shift element A and the fourth shift element D. In a secondexample variant 2.2, the second gear 2 results by engaging the fourthshift element D and the sixth shift element F. In a third examplevariant 2.3, the second gear 2 results by engaging the fifth shiftelement E and the sixth shift element F. Finally, the second gear 2 in afourth example variant 2.4 results by engaging the fourth shift elementD and the fifth shift element E.

In addition, a third gear can be implemented between the first inputshaft GW1 and the output shaft GWA in a first example variant 3.1 byactuating the first shift element A and the second shift element B. In asecond example variant 3.2, the third gear 3 can be implemented byactuating the second shift element B and the sixth shift element F. In athird example variant 3.3, the third gear 3 can be implemented byactuating the second shift element B and the fifth shift element E.

In a purely internal combustion engine-driven manner, the third gear canalso be implemented simply by engaging the second shift element B (V3).In the latter example variant V3, the electric machine EM 1 isdecoupled, and so travel can take place purely via the upstream internalcombustion engine VKM. By comparison, in the example variants 3.1through 3.3, travel takes place in a hybrid manner with simultaneousutilization of the internal combustion engine VKM and the electricmachine EM 1.

In addition, a fourth gear results between the first input shaft GW1 andthe output shaft GWA in a first example variant 4.1 by actuating thefirst shift element A and the third shift element C, wherein the fourthgear can also be implemented, in a second example variant 4.2, byengaging the third shift element C and the sixth shift element F and, ina third example variant 4.3, by engaging the third shift element C andthe fifth shift element E.

In a purely internal combustion engine-driven manner, the fourth gearcan also be implemented V4 simply by engaging the third shift element C.In the latter example variant V4, the electric machine EM 1 isdecoupled, and so travel can take place purely via the upstream internalcombustion engine VKM. By comparison, in the example variants 4.1through 4.3, travel takes place in a hybrid manner with simultaneousutilization of the internal combustion engine VKM and the electricmachine EM 1.

Although the shift elements A through F are each designed as form-fitshift elements, a power shift can be implemented between the first gear1 and the first example variant 2.1 of the second gear, between thefirst example variant 2.1 of the second gear 2 and the first examplevariant 3.1 of the third gear 3, and also between the first examplevariant 3.1 of the third gear 3 and the first example variant 4.1 of thefourth gear. The reason therefor is that the first shift element Acontributes to all these gears. A synchronization during the gear shiftscan take place in each case via an appropriate closed-loop control ofthe upstream internal combustion engine VKM, and therefore theparticular shift element to be disengaged is disengaged without load andthe shift element to be subsequently engaged can be engaged withoutload.

The example transmissions G from FIGS. 2 through 6 can also be operatedin alternative operating modes with the aid of the electric machine EM1.Purely electric driving can take place in a first gear E1, which iseffective between the second input shaft GW2 and the output shaft GWAand, for the implementation of which, the first shift element A is to betransferred into an engaged condition. As a result, when the first shiftelement A is engaged, the electric machine EM1 in the case of theexample transmissions G according to FIGS. 2 through 8 is coupled withthe output shaft GWA via a constant ratio (the particular third elementtransmits onto the particular second element with the particular firstelement of P2 and P3 fixed). The ratio of the first gear E1 correspondshere, in each case, to a ratio of the first gear 1 between the firstinput shaft GW1 and the output shaft GWA.

In addition, a second gear E2 can also be implemented between the secondinput shaft GW2 and the output shaft GWA, for the implementation ofwhich the sixth shift element F is to be engaged. As a result, theoutput shaft GWA in the example variants of the transmission G accordingto FIGS. 2 through 8 is coupled with the second input shaft GW2 and,thereby, also to the rotor R1 of the electric machine EM1 (the thirdelement E32 transmits onto the second element E22 with the first elementE12 of the third planetary gear set P3 fixed). A ratio of this secondgear E2 corresponds to a ratio of the second gear 2 between the firstinput shaft GW1 and the output shaft GWA.

Moreover, FIG. 8 shows a schematic of a transmission G according to afurther example embodiment of the invention, of the type which can alsobe utilized in the motor vehicle drive train in FIG. 1. This exampleembodiment essentially corresponds to the example variant according toFIG. 2, wherein, in contrast thereto, the first input shaft GW1 can nowbe rotationally fixed, at the mounting interface GW1-A via a seventhshift element K0, to a connection shaft AN, which is then connected tothe upstream internal combustion engine VKM in the motor vehicle drivetrain. The seventh shift element K0 is configured as a form-lockingshift element and, particularly preferably, is present as aconstant-mesh shift element. Moreover, a further electric machine EM2 isalso provided, the rotor R2 of which is rotationally fixed to the firstinput shaft GW1, while a stator S2 of the further electric machine EM2is fixed at the rotationally fixed component GG. For the rest, theexample variant according to FIG. 8 corresponds to the example designoption according to FIG. 2, and therefore reference is made to thedescription thereof. The seventh shift element K0 and the secondelectric machine EM2 do not have a functional relationship with oneanother, and so the two features can be combined with the exampleembodiment according to FIG. 2 independently of one another.

Moreover, FIG. 9 shows a schematic of a transmission G according to afurther example embodiment of the invention, of the type which can alsobe utilized in the motor vehicle drive train in FIG. 1. This exampleembodiment largely corresponds to the example variant according to FIG.8. In contrast thereto, the second electric machine EM2 is not providedat the first input shaft GW1, but rather at the third element E31 of thefirst planetary gear set P1. This means, the second rotor R2 isconnected to the third element E31 of the first planetary gear set P1 ina rotationally fixed manner. As a result, the first planetary gear setP1 acts as a transmission-internal pre-ratio. This means, the secondelectric machine EM2 rotates at a higher speed than the first inputshaft 1 and can therefore be designed with lower torque given the samepower, which provides advantages in terms of installation space as wellas costs. For the rest, the example variant according to FIG. 9corresponds to the example design option according to FIG. 8, andtherefore reference is made to the description thereof.

In FIG. 10, different conditions of the motor vehicle drive train fromFIG. 1, with utilization of the example transmission G from FIGS. 8 and9, are represented in table form, wherein these different conditions areachieved via different integrations of the two electric machines EM1 andEM2 and the internal combustion engine VKM.

Purely electric driving by a single electric machine and disengagedshift element K0. In the gear E1, purely electric driving takes placevia the electric machine EM1, in that the first gear E1 is implementedin the transmission G in the way described above with respect to FIG. 7.In the gear E2, purely electric driving also takes place via theelectric machine EM1, in that the second gear E2 is implemented in thetransmission G in the way described above with respect to FIG. 7. In thegear E3, purely electric driving takes place via the electric machineEM2, in that the third gear E3 is implemented in the transmission G byactuating the second shift element B. In the gear E4, purely electricdriving takes place via the electric machine EM2, in that the fourthgear E4 is implemented in the transmission G by actuating the thirdshift element C.

Purely electric driving with both electric machines and disengaged shiftelement K0. The same gear steps can be implemented as described in FIG.7, wherein these can now be driven purely electrically.

The advantages of two electric machines can be summarized as follows:

-   -   purely electric powershift, since the second electric machine        EM2, with disengaged shift element K0, performs the functions of        the internal combustion engine;    -   the second electric machine, with disengaged shift element K0,        can be utilized for synchronization, while the first electric        machine EM1 supports the tractive force;    -   a greater total electrical power is implementable with        disengaged shift element K0;    -   a greater range is possible in a hybrid operation;    -   the internal combustion engine VKM can be started by the second        electric machine EM2;    -   the second electric machine EM2 can synchronize the shift        element K0;    -   a battery-independent serial operation is possible; and    -   the second electric machine EM2 can be used as a generator, the        first electric machine can be used as a motor

With respect to the shift conditions during hybrid/during internalcombustion engine-driven travel, wherein the launch clutch K0 is engagedin this case, reference is made to the description related to FIG. 7.

Finally, FIGS. 11 through 16 show modifications of the exampletransmissions G from FIGS. 2 through 6 as well as 8, 9. Thesemodifications relate to alternative example possibilities forintegrating the electric machine EM1, although they can also beutilized, in a similar way, for the further electric machine EM2 in theexample transmissions G according to FIGS. 8, 9. In FIG. 11, forexample, the electric machine EM1 is not located coaxially to theparticular gear set RS (not represented in greater detail here) of thetransmission G, but rather is arranged axially offset with respectthereto. A connection takes place via a spur gear stage SRS, which iscomposed of a first spur gear SR1 and a second spur gear SR2. The firstspur gear SR1 is connected at the second input shaft GW2 in arotationally fixed manner on the side of the particular gear set RS. Thespur gear SR1 then meshes with the spur gear SR2, which is located on aninput shaft EW of the electric machine EM1 in a rotationally fixedmanner. Within the electric machine EM1, the input shaft EW establishesthe connection at the rotor (not represented further in this case) ofthe electric machine EM1.

In the case of the example modification according to FIG. 12 as well,the electric machine EM1 is located axially offset with respect to theparticular gear set RS of the particular transmission G. In contrast tothe preceding example variant according to FIG. 11, a connection is notestablished in this case via a spur gear stage SRS, however, but rathervia a flexible traction drive mechanism ZT. This flexible traction drivemechanism ZT can be configured as a belt drive or also a chain drive.The flexible traction drive mechanism ZT is then connected at the secondinput shaft GW2 on the side of the particular gear set RS. Via theflexible traction drive mechanism ZT, a coupling to an input shaft EW ofthe electric machine EM1 is then established. Within the electricmachine EM1, the input shaft EW establishes a connection at the rotor ofthe electric machine.

In the case of the example modification according to FIG. 13, anintegration of the electric machine EM1, which is located axially offsetwith respect to the particular gear set RS, is implemented via aplanetary gear stage PS and a spur gear stage SRS. The planetary gearstage PS is connected downstream from the gear set RS, wherein, on theoutput end of the planetary gear stage PS, the spur gear stage SRS isthen provided, via which the connection to the electric machine EM1 isestablished. The planetary gear stage PS is composed of a ring gear HO,a planet carrier PT, and a sun gear SO, wherein the planet carrier PTguides, in a rotatably mounted manner, at least one planet gear PR,which is meshed with the sun gear SO as well as with the ring gear HO.

In the present case, the planet carrier PT is connected at the secondinput shaft GW2 in a rotationally fixed manner on the side of the gearset RS from FIGS. 2 through 8 as well as 8, 9. By comparison, the ringgear HO is permanently fixed at the rotationally fixed component GG,while the sun gear SO is rotationally fixed to a first spur gear SR1 ofthe spur gear stage SRS. The first spur gear SR1 then meshes with asecond spur gear SR2 of the spur gear stage SRS, which is provided, in arotationally fixed manner, on an input shaft EW of the electric machineEM1. In this case, the electric machine EM1 is therefore connected bythe gear set RS via two gear stages.

In the case of the example modification from FIG. 14 as well, anintegration of the electric machine EM1 is implemented by the gear setRS via a planetary gear stage PS and a spur gear stage SRS. Themodification largely corresponds to the variant according to FIG. 13,with the difference that, with respect to the planetary gear stage PS,the sun gear SO is now fixed at the rotationally fixed component GG,while the ring gear HO is rotationally fixed to the first spur gear SR1of the spur gear stage SRS. Specifically, the ring gear HO and the firstspur gear SR1 are preferably designed as one piece, in that the ringgear HO is equipped, at an outer circumference, with a tooth system. Forthe rest, the example modification according to FIG. 14 corresponds tothe example variant according to FIG. 13, and therefore reference ismade to the description thereof.

Moreover, FIG. 15 shows one further example modification of thetransmissions G from FIGS. 2 through 6 as well as 8, 9, wherein, in thiscase as well, an integration of the electric machine EM1 is implementedvia a spur gear stage SRS and a planetary gear stage PS. In contrast tothe preceding example variant according to FIG. 14, the gear set RS isinitially followed here by the spur gear stage SRS, while the planetarygear stage PS is provided in the power flow between the spur gear stageSRS and the electric machine EM1. The planetary gear stage PS alsoincludes, once again, the elements ring gear HO, planet carrier PT, andsun gear SO, wherein the planet carrier PT guides, in a rotatablymounted manner, multiple planet gears PR1 and PR2, each of which ismeshed with the sun gear SO as well as with the ring gear HO.

As is apparent in FIG. 15, a first spur gear SR1 of the spur gear stageSRS is connected in a rotationally fixed manner on the side of the gearstage RS of the transmissions G from FIGS. 2 through 6 as well as 8, 9,wherein this connection is completed at the second input shaft GW2. Thefirst spur gear SR1 then meshes with a second spur gear SR2 of the spurgear stage SRS, which is rotationally fixed to the planet carrier PT ofthe planetary gear stage PS. The ring gear HO is permanently fixed atthe rotationally fixed component GG, while the sun gear SO is provided,in a rotationally fixed manner, on an input shaft EW of the electricmachine EM1.

Finally, FIG. 16 shows one further example modification of thetransmissions G from FIGS. 2 through 6 as well as 8, 9, wherein thismodification essentially corresponds to the preceding example variantaccording to FIG. 15. The only difference is that the sun gear SO of theplanetary gear stage PS is now permanently fixed at the rotationallyfixed component GG, while the ring gear HO of the planetary gear stagePS is rotationally fixed to the input shaft EW of the electric machineEM1. For the rest, the example modification according to FIG. 16corresponds to the example variant according to FIG. 15, and thereforereference is made to the description thereof.

By the example embodiments according to the invention, a transmissionhaving a compact design and good efficiency can be implemented.

The invention was comprehensively described and explained with referenceto the drawings and the description. The description and the explanationare to be understood as an example and are not to be understood aslimiting. The invention is not limited to the disclosed embodiments.Other embodiments or variations result for a person skilled in the artwithin the scope of the utilization of the present invention and withinthe scope of a precise analysis of the drawings, the disclosure, and thefollowing claims. For example, in particular, the interlock variants forthe second shift element are arbitrarily combinable with the interlockvariants for the sixth shift element.

In the claims, the words “comprise” and “comprising” do not rule out thepresence of further elements or steps. The indefinite article “a” doesnot rule out the presence of a plurality. A single element or a singleunit can carry out the functions of several of the units mentioned inthe claims. The mere mention of a few measures in multiple variousdependent claims is not to be understood to mean that a combination ofthese measures cannot also be advantageously utilized.

Modifications and variations can be made to the embodiments illustratedor described herein without departing from the scope and spirit of theinvention as set forth in the appended claims. In the claims, referencecharacters corresponding to elements recited in the detailed descriptionand the drawings may be recited. Such reference characters are enclosedwithin parentheses and are provided as an aid for reference to exampleembodiments described in the detailed description and the drawings. Suchreference characters are provided for convenience only and have noeffect on the scope of the claims. In particular, such referencecharacters are not intended to limit the claims to the particularexample embodiments described in the detailed description and thedrawings.

REFERENCE CHARACTERS

-   G transmission-   RS gear set-   GG rotationally fixed component-   P1 first planetary gear set-   E11 first element of the first planetary gear set-   E21 second element of the first planetary gear set-   E31 third element of the first planetary gear set-   P2 second planetary gear set-   E12 first element of the second planetary gear set-   E22 second element of the second planetary gear set-   E32 third element of the second planetary gear set-   P3 third planetary gear set-   E13 first element of the third planetary gear set-   E23 second element of the third planetary gear set-   E33 third element of the third planetary gear set-   A first shift element-   B second shift element-   C third shift element-   D fourth shift element-   E fifth shift element-   F sixth shift element-   K0 seventh shift element-   SP1 shift element pair-   SP2 shift element pair-   SP3 shift element pair-   1 first gear-   2.1 second gear, first variant-   2.2 second gear, second variant-   2.3 second gear, third variant-   2.4 second gear, fourth variant-   3.1 third gear, first variant-   3.2 third gear, second variant-   3.3 third gear, third variant-   V3 third gear, internal combustion engine-driven-   4.1 fourth gear, first variant-   4.2 fourth gear, second variant-   4.3 fourth gear, third variant-   V4 fourth gear, internal combustion engine-driven-   E1 first gear, electric-   E2 second gear, electric-   GW1 first input shaft-   GW1-A mounting interface-   GW2 second input shaft-   GWA output shaft-   GWA-A mounting interface-   AN connection shaft-   EM1 electric machine-   S1 stator-   R1 rotor-   EM2 electric machine-   S2 stator-   R2 rotor-   SRS spur gear stage-   SR1 spur gear-   SR2 spur gear-   PS planetary gear stage-   HO ring gear-   PT planet carrier-   PR planet gear-   PR1 planet gear-   PR2 planet gear-   SO sun gear-   ZT flexible traction drive mechanism-   VKM internal combustion engine-   TS torsional vibration damper-   AG differential gear-   DW driving wheels

The invention claimed is:
 1. A transmission (G) for a motor vehicle,comprising: an electric machine (EM1); a first input shaft (GW1); asecond input shaft (GW2); an output shaft (GWA); a first planetary gearset (P1), a second planetary gear set (P2), and a third planetary gearset (P3), each of the first, second and third planetary gear sets (P1,P2, P3) comprising a respective plurality of elements (E11, E21, E31,E12, E22, E32, E13, E23, E33); and a first shift element (A), a secondshift element (B), a third shift element (C), a fourth shift element(D), a fifth shift element (E), and a sixth shift element (F), wherein arotor (R1) of the electric machine (EM1) is connected to the secondinput shaft (GW2), wherein the first input shaft (GW1) is rotationallyfixed to a second element (E21) of the first planetary gear set (P1),wherein the output shaft (GWA) is rotationally fixed to a second element(E23) of the third planetary gear set (P3), wherein a first element (El1) of the first planetary gear set (P1) and a first element (El 3) ofthe third planetary gear set are fixed to a rotationally fixed component(GG), wherein the second planetary gear set (P2) comprises a firstcoupling of a first element (E12) of the second planetary gear set (P2)with the rotationally fixed component (GG), a second coupling of asecond element (E22) of the second planetary gear set (P2) with a thirdelement (E33) of the third planetary gear set (P3), and a third couplingof a third element (E32) of the second planetary gear set (P2) with thesecond input shaft (GW2), and two couplings of the first, second, andthird couplings of the second planetary gear set (P2) are rotationallyfixed connections, while the remaining couplings of the first, second,and third couplings of the second planetary gear set (P2) is arotationally fixed connection establishable by the first shift element(A, A′, A″), wherein the second shift element (B) is configured foreither connecting the output shaft (GWA) to the input shaft (GW1) orconnecting the second input shaft (GW2) to the third element (E33) ofthe third planetary gear set (P3), wherein the third shift element (C)is configured for rotationally fixing the output shaft (GWA) to thethird element (E31) of the first planetary gear set (P1), wherein thefourth shift element (D) is configured for rotationally fixing the firstinput shaft (GW1) to the third element (E33) of the third planetary gearset (P3), wherein the fifth shift element (E) is configured forrotationally fixing the first input shaft (GW1) to the second inputshaft (GW2), and wherein the sixth shift element (F, F′, F″) isconfigured for interlocking the second planetary gear set (P2).
 2. Thetransmission (G) of claim 1, wherein, by selective engagement of the sixshift elements (A, B, C, D, E, F): a first gear (1) results between thefirst input shaft (GW1) and the output shaft (GWA) by actuating thefirst shift element (A) and the fifth shift element (E); a second gearresults between the first input shaft (GW1) and the output shaft (GWA)in a first variant (2.1) by actuating the first shift element (A) andthe fourth shift element (D), in a second variant (2.2) by actuating thefourth shift element (D) and the sixth shift element (F), in a thirdvariant (2.3) by actuating the fifth shift element (E) and the sixthshift element (F), and in a fourth variant (2.4) by actuating the fourthshift element (D) and the fifth shift element (E); a third gear resultsbetween the first input shaft (GW1) and the output shaft (GWA) in afirst variant (3.1) by actuating the first shift element (A) and thesecond shift element (B), in a second variant (3.2) by actuating thesecond shift element (B) and the sixth shift element (F), and in a thirdvariant (3.3) by actuating the second shift element (B) and the fifthshift element (E); and a fourth gear results between the first inputshaft (GW1) and the output shaft (GWA) in a first variant (4.1) byactuating the first shift element (A) and the third shift element (C),in a second variant (4.2) by engaging the third shift element (C) andthe sixth shift element (F), and in a third variant (4.3) by actuatingthe third shift element (C) and the fourth shift element (D).
 3. Thetransmission (G) of claim 1, wherein: a first gear (E2) results betweenthe second input shaft (GW2) and the output shaft (GWA) by engaging thefirst shift element (A); and a second gear (E2) results between thesecond input shaft (GW2) and the output shaft (GWA) by actuating thesixth shift element (F).
 4. The transmission (G) of claim 1, wherein thefirst, second, and third planetary gear sets (P1, P2, P3) are arrangedin an axial direction starting from a transmission input in the sequencefirst planetary gear set (P1), second planetary gear set (P2), thirdplanetary gear set (P3).
 5. The transmission (G) of claim 1, furthercomprising an additional electric machine (EM2), a rotor (R2) of theadditional electric machine (EM2) connected at the first input shaft(GW1).
 6. The transmission (G) of claim 1, further comprising anadditional electric machine (EM2), a rotor (R2) of the additionalelectric machine (EM2) connected at the third element (E13) of the firstplanetary gear set (P1).
 7. The transmission (G) of claim 1, furthercomprising a seventh element (K0), the first input shaft (GW1)rotationally fixable to a connection shaft (AN) via the seventh element(K0).
 8. The transmission (G) of claim 1, wherein one or more of the sixshift elements (A, B, C, D, E, F, K0) is a form-locking shift element.9. The transmission (G) of claim 1, wherein the rotor (R1) of theelectric machine (EM1) is rotationally fixed to the second input shaft(GW2) or is connected to the second input shaft (GW2) via at least onegear stage.
 10. A motor vehicle drive train for a hybrid or electricvehicle, comprising the transmission (G) of claim
 1. 11. A method foroperating the transmission (G) of claim 1, wherein only the fifth shiftelement (E) is engaged in order to implement a charging operation or astarting operation.